LONDON • A year may have passed but the scar still causes pain. For Arsene Wenger, the nightmare of last season's Champions League exit continues to rankle.

Almost 12 months to the day since one of the club's most chastening nights in Europe, when Arsenal's naivety was exposed, Wenger has urged his players to learn the error of their ways.

A 3-1 home defeat by Monaco in the first leg of their round-of-16 tie was perhaps one of the most embarrassing nights the English football club have endured in the Frenchman's 19-year tenure.

"In these big games, in the first tie at home, we can't be stupid," he said. "Many times we've won away and at home we've conceded. We have to find a good balance between defending and attacking."

Arsenal did manage to score twice without reply in the return leg but still bowed out of the competition on the away-goals rule, a result that provided a lengthy period of introspection for players and manager alike.

That defeat by Monaco is etched on Wenger's mind, particularly before today's first leg of their Champions League last 16 game with Barcelona, a team who have the ability to win the tie inside five minutes.

He is aware of his side's inability to keep a clean sheet at home in the first knockout phase. In 2013, Bayern Munich won 3-1 in a first-leg win at the Emirates and progressed to the quarter-final despite Arsenal winning 2-0 in the return fixture.

A year later, Bayern won 2-0 in London before securing a 1-1 draw in Germany.

This season's tie with Barcelona, boasting arguably the best front three the Spanish club have possessed for many years, will be one of the most challenging yet.

As a combination, Lionel Messi, Luis Suarez and Neymar have scored 91 goals this season.

Wenger says that he does not ponder what could have been if Arsenal had been successful in luring Suarez to Arsenal from Liverpool with that infamous offer of £40,000,001 (S$79,179,925) in 2013.

He has been impressed by the forward's ability to gel with Messi and Neymar, ensuring that the front three bring out the best in each other.

Wenger says that Suarez, who scored his 41st goal of the season in Barcelona's 2-1 win away to Las Palmas on Saturday, has brought camaraderie to the Catalan side's attack.

The Frenchman believes that is illustrated by Messi's decision to pass to Suarez from the penalty spot rather than shooting to secure what would have been his 300th La Liga goal.

"Suarez is the kind of guy who manages to create that spirit in teams," Wenger said. "He did it at Liverpool, he did it playing with Cavani and Forlan (for Uruguay), and did it well.

"I believe that, apart from the individual talent the three have, they have a good understanding and cohesion. They have a great solidarity. They don't look to play under any pressure because they know at the moment it's easy for them."

It is not difficult to imagine why those in Barcelona shirts are playing with smiles on their faces. They are unbeaten in 32 matches and have won their past eight league games.

They are playing a brand of football that even the most cynical and hard-hearted of aficionados will applaud. Not since the start of October, when Luis Enrique's men were beaten 2-1 away to Sevilla, have they tasted defeat.

Barcelona, though, must iron out some defensive issues that were posed by a creative Las Palmas side, who came close to snatching a late equaliser.

Enrique will be boosted by the return of defender Gerard Pique, who was rested at the weekend, and defensive midfielder Sergio Busquets from suspension.

So what chances do Arsenal have?

"I don't know," Wenger, who will have German playmaker Mesut Oezil and midfielder Aaron Ramsey back for the match, said with a wry smile. "It's our best chance, no matter how big the chance is. We have to take it and have a go at them.

"We'll need great solidarity because we'll need to defend well, and make the maximum of our possession."

THE TIMES, LONDON, REUTERS, AGENCE FRANCE-PRESSE

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